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Premedication

Use of premedication can decrease patient stress and anxiety, improve the ease of patient handling, improve muscle relaxation and decrease the requirements for the most potent anaesthetic drugs. As a result, a smoother anaesthetic induction, transition and recovery can be achieved.

Premedications

A range of medications are commonly used in the premedication period including;

  • Phenothiazines (acepromazine)
  • Benzodiazepines (diazepam, midazolam)
  • Alpha-2-adrenoreceptor agonists (medetomidine, dexmedetomidine)
  • Opioids (methadone, buprenorphine, morphine, butorphanol)
  • NSAIDS (carprofen, meloxicam)
  • (Anticholinergic agents (atropine))

Premedication effects on the anaesthesia

Successful premedication smooths the stages of anaesthesia - induction, transition, maintenance and recovery.  The pre-anaesthetic period requires focus and the careful selection of the most appropriate premedication tailored to the individual patient.

Reducing stress for the patient (and clinic personnel) during the pre-anaesthetic period is essential.  This may be achieved with a combination of a quiet, calm environment,  considerate patient handling and the use of  suitably selected sedatives and analgesics.

Some premedicants have greater or lesser effect on the anaesthetic. For example, alpha-2 agonists (medetomidine, dexmedetomidine) may decrease the required dose of Alfaxan and increase the circulation time. As a result it may be necessary to administer Alfaxan more slowly and a lower dose than calculated may be required to induce anaesthesia. Alpha-2 agonists may also increase the duration of anaesthesia, particularly in sighthounds. 43 

Analgesia is an important aspect of premedication. Selection of the most suitable analgesic should take into consideration the species and breed of animal, the type of procedure and degree of pain expected, the level of analgesia provided by the drug and the length of the expected analgesic effect from the drug.

Selecting the most appropriate route of administration is necessary to ensure maximum response to the premedicant. The intramuscular and intravenous routes, where licensed for the specific drug, are the ideal. As a component of best practice, Jurox encourages veterinarians to make placement of an intravenous catheter prior to anaesthetic induction a standard practice.

Allowing sufficient time for premedicants to take effect is essential for ensuring smooth anaesthetic induction.

Alfaxan® has been shown to be safe when used with a wide range of premedicant drugs. 26-35, 38, 39, 42-44, 53, 54

Veterinary surgeons should assess each patient's individual requirements and tailor the selection of premedicant drugs to that specific animal thus avoiding 'blanket' premed regimes.

Premedication Agents Veterinary surgeons have access to a wide range of premedicant drugs and protocols.
Alfaxan has safely been used with a wide range of premedicant drugs. 26-35, 38, 39, 42-44, 53, 54

Drug Time to peak sedaction or effect Duration of action Reversible? Analgesia?

*Note that the duration of action of many of these drugs will vary between species, the route and dose administered, the health status of the patient and any concurrent medication.  The times given are approximate guidelines only. 

Reproduced with permission from the BSAVA Manual of Canine and Feline Anaesthesia and Analgesia, 3rd edition, © BSAVA
Acepromazine 35-40 minutes i.m.
15-20 minutes i.v.
4-6 hours No No
Medetomidine
Dexmedetomidine
15-20 minutes i.m.
2-3 minutes i.v.
Sedation: 2-3 hours
Analgesia: 1 hour
Yes – with atipamezole Yes
Midazolam 10-15 minutes i.m.
5 minutes i.v.
1-1.5 hours Yes – with flumazenil No
Diazepam 10-15 minutes i.m.
5 minutes i.v.
2 hours Yes – with flumazenil No
Atropine 20-30 minutes i.m.
1-2 minutes i.v.
Vagal inhibition: 60-90 minutes No No
Glycopyrronium 20-30 minutes i.m.
2-3 minutes i.v.
Vagal inhibition: 2-3 hours No No
Methadone
20-30 minutes i.m.
2-5 minutes i.v.
2-4 hours Yes – with naloxone Yes
Morphine 20-30 minutes i.m.
Not recommended i.v.
2-4 hours Yes – with naloxone Yes
Pethidine
20-30 minutes i.m.
Contraindicated i.v.
1-1.5 hours Yes – with naloxone Yes
Buprenorphine 30-45 minutes i.m.
12-15 minutes i.v.
6 hours Yes – with naloxone Yes
Butorphanol 20-30 minutes i.m.
2-5 minutes i.v.
1-1.5 hours Yes – with naloxone Yes
Repeatable. Reliable. Relax.